1. Field of the Invention
The present invention relates to a voltage divider circuit which outputs a voltage between first and second voltages, and a differential amplifier circuit which outputs a voltage converted a voltage level of a differential input voltage. More specifically, the present invention relates to a circuit which can be formed on a semiconductor substrate.
2. Related Background Art
When a plurality of resistors are connected in series, with one end of those resistors being connected to a power supply voltage, and with the other end being grounded, it is possible to produce a divided voltage. Such a circuit is called a divider circuit. The circuit is used for various objects, because the circuit has a simple configuration.
In case of forming a divider circuit on a semiconductor substrate, it is customary to form resistors using poly-silicon. However, it is difficult to form resistors with high resistance using poly-silicon. Further, when the divider circuit is formed by using poly-silicon, it is necessary to change the production process in order to change the divided resistance ratio of the divider circuit. That is, it is not easy to change a voltage level of the divided voltage after the production process had been performed, because it is necessary to change the width and thickness of a poly-silicon layer by revising a photo mask and so on.
On the other hand, it is possible to replace the resistors by MOS transistors. However, even if the resistors are replaced by MOS transistors, it is impossible to obtain high accurate resistance ratio due to distortion of a threshold voltage Vth and so on.